The present invention relates to an assembly with a base board and at least one daughter board, in particular an assembly of this kind in which the base board includes at least one attachment means for attaching the base board to a mainframe.
The problem to be solved by the present invention is described in the following with reference to FIG. 1. FIG. 1 is a schematic view of a prior art base board 10 including two daughter boards 12a, 12b of which, however, only the electrically conductive front panels 14a and 14b are shown in the view of FIG. 1. The assembly consisting of the base board 10 and the daughter boards 12a, 12b is of a standardized width B and a standardized height H. These may for example correspond to the IEEE 1101 standard designed for the cPCI bus system or the VME bus.
The shortcoming of this prior art assembly is that the maximum admissible width of the connectors on the daughter boards 12a, 12b is restricted by the width b of the front panel 14a, 14b of the daughter board, which is less than the standardized width B. In such a case, merely installing a conventional BNC connector may already cause problems. Another problem results from the requirement to electrically connect the front panels 14a, 14b to the front 16 of the base board 10. This makes high demands on the manufacturing quality, with regard to the cutting out of the front panel 16 of the base board 10 as well as of the front panels 14a, 14b of the daughter boards 12a, 12b. It is known to insert metallically conductive seals in the gap between the front panel 14a, 14b of the daughter board 12a, 12b and the front panel 16 of the base board 10. However, such seals either have good electricity conducting properties or they are resilient. This makes it difficult to obtain a transition between the front panel 14a, 14b of the daughter boards 12a, 12b and the front panel 16 of the base board 10 which conducts well and seals tightly. Insufficient sealing moreover causes an EMI problem in that electromagnetic radiation may exit through the gaps between the front panels of the daughter board and that of the base board, thus causing interference.
For this reason, it is the object of the present invention to enhance the aforementioned assembly in such a way that it allows the use of as wide as possible connectors on the daughter board while reducing the EMI problem.
This object is accomplished by the present invention by providing an assembly with a base board and at least one daughter board, in particular an assembly of this kind in which the base board includes at least one attachment means for attaching the base board to a mainframe. In this case the front of the assembly, which remains accessible from the exterior once the assembly has been installed in a mainframe, is of a standardized width. The daughter board is connected to the base board via at least a second attachment means in such a way that an electrically conductive daughter board front panel forms at least a portion of the front of the assembly. With the aforementioned assembly, at least a portion of the front panel of the daughter board is of the standardized width.
The present invention is based on the idea that the abovementioned problems can be avoided if the daughter board front panel itself constitutes the assembly front panel at a certain height and along a certain portion. This allows the daughter board front panel to be made as wide as permitted under the standard, for which purpose the same connectors can be chosen for the daughter board as for the base board. The fact that the standardized width is much smaller than the gaps extending in the direction of the height of the prior art assembly clearly reduces the EMI problem.
The fact that the front panel of the daughter board no longer has to be fitted into the front panel of the base board, in particular the edges of the daughter boards can be straight, makes production much easier, which in turn clearly reduces production costs.
In a particularly preferred embodiment, the daughter board front panel is of uniform thickness, except for through-holes and/or EMI flanges. Producing daughter board front panels of uniform thickness is especially simple and thus inexpensive.
It is preferred to have the daughter board front panel coupled to a portion of the base board which constitutes a portion of the front of the assembly via an electrically conducting coupling element. Such a coupling element may be generously designed so that good electrical contact is achieved between the daughter board front panels and the portion of the base board which forms a portion of the front of the assembly. In particular, the rear of the daughter board front panel may for example be used here, in order to make the latter contact the coupling element over a certain area, whereas the prior art only used the contact surfaces which were very small owing to the thickness of the front panel.
The daughter board front panel is preferably connected to the front panel of at least one further daughter board via an electrically conducting coupling element, which at least one further daughter board likewise constitutes a portion of the front of the assembly. In this variant, a coupling element can be used for obtaining an electrically conducting connection between several daughter boards and a portion of the front of the assembly which is constituted by the base board.
The coupling element may be of the U- or block-shaped type. In this case, one side of the U-shaped or block-shaped element may be connected to the base board, with the respective other side thereof being connected to at least one electrically connecting daughter board front panel. In such a design, the coupling element not only serves for obtaining an electrical connection, but also for stably mounting the daughter board on the assembly.
The assembly may especially meet the requirements of a mechanical assembly pursuant to the IEEE 1101 standard.
The side of the daughter board abutting the front of the assembly and facing away from the coupling means may be connected to the base board via a third attachment means. Said third attachment means may be in the form of a bolt, thus providing a simple means for reliably connecting the daughter board to the base board.
In a preferred embodiment, the front panel of the at least one daughter board is of the standardized width over its entire length. This allows the front panel to be made of rectangular shape which will result in a particularly easy manufacture and thus low assembly costs. In this embodiment, each daughter board front panel then forms a height portion of the front of the assembly.
Further advantageous embodiments of the invention can be gathered from the subclaims.